Amoxicillin Resistance: An In Vivo Study on the Effects of an Approved Formulation on Antibiotic Resistance in Broiler Chickens
<b>Background:</b> Antimicrobial resistance (AMR) is a growing global concern in poultry production, where antibiotic use can disrupt gut microbiota and enrich antimicrobial resistance genes (ARGs). <b>Objectives:</b> This study aimed to assess the in vivo effects of a veteri...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-07-01
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| Series: | Animals |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2076-2615/15/13/1944 |
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| Summary: | <b>Background:</b> Antimicrobial resistance (AMR) is a growing global concern in poultry production, where antibiotic use can disrupt gut microbiota and enrich antimicrobial resistance genes (ARGs). <b>Objectives:</b> This study aimed to assess the in vivo effects of a veterinary-approved amoxicillin formulation on gut microbiome composition and ARG profiles in broiler chickens. <b>Methods:</b> A total of 120 Ross-308 broiler chickens were randomly allocated into 12 experimental groups (<i>n =</i> 10 per group), with three replicates per treatment. Birds received either full-dose (1×), a subtherapeutic quarter-dose (¼×) of amoxicillin, a placebo (starch), or no treatment. Cloacal swabs were collected on days 0, 14, and 28 for shotgun metagenomic sequencing. One-way ANOVA was used to evaluate treatment effects on body weight, with significant differences observed from day 14 onward (<i>p</i> < 0.0001). <b>Results:</b> The ¼× dose caused a more pronounced microbiome shift than the 1× dose, with a marked reduction in Pseudomonadota and increase in Bacillota and Bacteroidota. ARG abundance declined in the ¼× group (from 1386 to 1012). While TEM-type ESBL genes were ubiquitous, <i>CTX-M-1</i> emerged only after ¼× treatment. Worryingly, 20 types of vancomycin resistance genes were detected across all samples. Plasmid-borne ARGs and mobile genetic elements decreased in the ¼× group. <b>Conclusions:</b> Even subtherapeutic antibiotic exposure significantly reshapes the gut microbiota composition and ARG landscape, highlighting the need for refined risk assessments and microbiome-conscious antimicrobial policies in poultry farming. |
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| ISSN: | 2076-2615 |